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Questions and Answers
What role do chemoreceptors play in the control of ventilation?
What role do chemoreceptors play in the control of ventilation?
How do baroreceptors contribute to respiratory control?
How do baroreceptors contribute to respiratory control?
Which of the following gases is most relevant for chemoreceptors during ventilation control?
Which of the following gases is most relevant for chemoreceptors during ventilation control?
What is the impact of irritants and noxious fumes on respiration?
What is the impact of irritants and noxious fumes on respiration?
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What is the normal range for arterial blood carbon dioxide pressure (PaCO2)?
What is the normal range for arterial blood carbon dioxide pressure (PaCO2)?
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Which component in ventilation control prevents over-inflation of the lungs?
Which component in ventilation control prevents over-inflation of the lungs?
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The normal range for systemic arterial blood pH is approximately:
The normal range for systemic arterial blood pH is approximately:
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Which gas's partial pressure is lower in atmospheric air compared to arterial blood?
Which gas's partial pressure is lower in atmospheric air compared to arterial blood?
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What role do central chemoreceptors primarily play in respiration?
What role do central chemoreceptors primarily play in respiration?
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What is the effect of increased carbon dioxide levels in the blood on respiration?
What is the effect of increased carbon dioxide levels in the blood on respiration?
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Where are peripheral chemoreceptors located?
Where are peripheral chemoreceptors located?
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What happens to ventilation when blood pressure falls?
What happens to ventilation when blood pressure falls?
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How does the body respond to low oxygen levels in terms of ventilation?
How does the body respond to low oxygen levels in terms of ventilation?
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Which of the following is a primary factor detected by peripheral chemoreceptors?
Which of the following is a primary factor detected by peripheral chemoreceptors?
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Which brain structures are primarily responsible for voluntary control of respiration?
Which brain structures are primarily responsible for voluntary control of respiration?
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What mechanism allows the body to alter respiratory rate and depth in response to physical activity?
What mechanism allows the body to alter respiratory rate and depth in response to physical activity?
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What is indicated by the term 'tidal volume' in respiratory physiology?
What is indicated by the term 'tidal volume' in respiratory physiology?
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What is the primary function of baroreceptors in relation to respiration?
What is the primary function of baroreceptors in relation to respiration?
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What is the normal range for respiratory rate per minute in adults?
What is the normal range for respiratory rate per minute in adults?
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How is minute volume calculated?
How is minute volume calculated?
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What does alveolar ventilation measure?
What does alveolar ventilation measure?
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What calculation is used to determine the effect of shallow breathing on anatomical dead space?
What calculation is used to determine the effect of shallow breathing on anatomical dead space?
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What is the relationship between FEV1 and FVC in healthy adults?
What is the relationship between FEV1 and FVC in healthy adults?
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Which of the following lung volumes represents the maximum amount of air that can be exhaled after a normal expiration?
Which of the following lung volumes represents the maximum amount of air that can be exhaled after a normal expiration?
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Which lung capacity is defined as the total volume of air in the lungs after a maximal inhalation?
Which lung capacity is defined as the total volume of air in the lungs after a maximal inhalation?
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What is primarily measured using spirometry?
What is primarily measured using spirometry?
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Which factor can lead to failure to ventilate the lungs adequately?
Which factor can lead to failure to ventilate the lungs adequately?
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What does residual volume refer to in lung volumes?
What does residual volume refer to in lung volumes?
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Study Notes
Transport of Oxygen & Carbon Dioxide
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Oxygen Transport:
- Occurs in three stages:
- Diffusion of O₂ from alveoli into pulmonary blood.
- Transport of blood through arteries to tissue capillaries.
- Diffusion of O₂ from the capillaries to tissue cells.
- Occurs in three stages:
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Oxygen Carriage:
- Majority of oxygen is carried in red blood cells on iron/haem molecules in haemoglobin.
- 1.5% is dissolved in the plasma.
- Oxyhaemoglobin = Hb saturated with O₂
- Deoxyhaemoglobin = Hb without O₂
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Haemoglobin Structure:
- Each haemoglobin protein consists of 4 haem molecules.
- Each haem molecule combines with 2 oxygen molecules (Hb₄O₈).
- Each red blood cell carries ~280 million Hb proteins.
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Haemoglobin Function:
- Uploads O₂ when plentiful.
- Easily transports O₂ without offloading unnecessarily.
- Offloads O₂ when needed, adjusting the amount to meet demand.
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Oxygen Saturation:
- Measured as SaO₂ (arterial O₂ saturation) by a blood gas machine or SpO₂ (peripheral O₂ saturation) by a pulse oximeter.
- Normal value is 95-99%.
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Gaseous Pressure in Alveoli & Blood:
- Alveolar air: O₂ = ~104mmHg/14kPa, CO₂ = ~40mmHg/5.3kPa, N₂=~569mmHg/78kPa.
- Venous blood: O₂ = ~40mmHg/5.3kPa, CO₂ = ~45mmHg/6kPa, N₂ = ~569mmHg/78kPa.
- Arterial blood: O₂ = ~100mmHg/13.3kPa, CO₂ = ~40mmHg/5.3kPa, N₂ = ~569mmHg/78kPa
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Affinity:
- Affinity is binding ability.
- As O₂ binds to Hb, affinity for O₂ increases.
- As O₂ is released, Hb affinity for O₂ decreases.
- High affinity helps pick up O₂ in the lungs.
- Lower affinity helps release O₂ to tissues.
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Partial Pressure:
- Partial pressure is the pressure a gas would exert if it occupied the space alone.
- Total pressure of a gas mixture is the sum of the partial pressures of individual gases in the mixture.
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Oxygen Dissociation Curve:
- Shows the percentage of haemoglobin combined with oxygen at different oxygen pressures.
- Lower partial pressure of oxygen (pO₂), lower affinity of Hb for O₂ and O₂ is released to tissues.
Other Considerations
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Myoglobin:
- Oxygen storage protein in slow-twitch skeletal and cardiac muscle.
- Stores 1/4 the amount of oxygen as haemoglobin.
- Important in initial phase of exercise to supply mitochondria with oxygen.
- Important in oxygen supply to heart muscle during systole and coronary occlusions.
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Fetal Haemoglobin:
- Higher affinity for oxygen than adult haemoglobin.
- Facilitates oxygen transfer from maternal blood to fetal blood in the placenta.
Carbon Dioxide Transport
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Carbon Dioxide Transport:
- 70% transported as bicarbonate ions (HCO₃⁻).
- 10% dissolved as gas molecules directly in the blood.
- 20% as carbaminohaemoglobin, bound to Hb.
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CO₂ Equation:
- CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃⁻
- Carbon dioxide and water react reversibly to form carbonic acid, which dissociates into hydrogen ions and bicarbonate ions.
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Haldane Effect:
- The lower the PO₂ (and Hb saturation with O₂), the more CO₂ can be carried by the Hb.
- Deoxyhaemoglobin has a higher affinity for CO₂ than oxyhaemoglobin.
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CO₂ and O₂ exchange in the lungs and tissues:
- At the lungs, CO₂ diffuses from blood into alveolar air.
- At the tissues, CO₂ diffuses from tissue cells into blood.
Partial Pressures of O₂ and CO₂ in Blood and Alveoli
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Arterial Blood Gases:
- pH: 7.35 - 7.45
- PaCO₂: 4.6 - 6.0 kPa (35 – 45 mmHg)
- PaO₂: 11 - 14 kPa (80 – 100 mmHg)
- HCO₃⁻: 22 – 26 mmol/L
- SaO₂: 95–98%
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Venous Blood Gases:
- pH: 7.34 - 7.37
- PvCO2: 5.8 – 6.1 kPa (44 – 46 mmHg)
- PvO2: 5.0 – 5.5 kPa (38 – 42 mmHg)
- HCO₃⁻: 24 – 30 mmol/L
- SvO₂: ~75%
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Ventilation Control:
- Respiratory centres: Chemoreceptors (peripheral and central), Baroreceptors in the aortic arch, Stretch receptors that prevent overinflation.
- Reaction to irritants: Irritants in the respiratory tract trigger reactions like coughing, sneezing, and laryngospasm.
- Voluntary control: Anticipation of exercise, and partial control.
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Control of respiratory rate and depth: Respiratory centers in the brainstem set the rate and depth of breathing. Centres receive input from sensory neurons to alter the ventilatory pattern.
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Chemoreceptors: Measure pH and levels of gases in blood. Central Receptors: Medullary receptors sensitive to H+ and rise in CO2 increases rate & depth of breath. Peripheral Receptors in the aortic and carotid bodies are sensitive to lower P02, increased PCO2 & increased H+.
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Baroreceptors: measure blood pressure. When blood pressure falls, ventilation increases and vice versa.
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Description
This quiz explores the mechanisms involved in the transport of oxygen and carbon dioxide in the human body. It covers the stages of oxygen transport, the role and structure of hemoglobin, and how oxygen saturation is measured. Test your knowledge on how these processes work together to maintain proper physiological function.
